Hydrostatic radial bearing

ABSTRACT

A hydrostatic radial bearing having a housing with successive bearing segments in the circumferential direction. Each bearing segment comprises a pressure chamber and a raised edge which surrounds said chamber and together with the rotatable shaft forms an outflow gap. The pressure chambers are located partly beside each other and overlap each other in the circumferential direction. The outflow gaps have a resistance to flow which is variable in the circumferential direction; the resistance to flow varies in such manner that the forces exerted on the shaft by the pressure chambers, in response to a localized unevenness with respect to an imaginary line joining the center of the bearing to the center of one of the bearing segments.

United States Patent [191 Ferguson Sept. 25, 1973 HYDROSTATIC RADIALBEARING Primary Examiner-Charles J. Myhre [75] Inventor: Eric TapleyFerguson, Emmasingel, Assistant Exammer Fram,( Susko Eindhoven-Netherlands 7 Attorney-Frank R. Trifari [73] Assignee: U.S. PhilipsCorporation, New York,

NY [57] ABSTRACT [22] Fil d; S 27, 1971 A hydrostatic radial bearinghaving a housing with successive bearing segments in the circumferentialdirec- [21 1 Appl ls3764 tion. Each bearing segment comprises a pressurechamber and a raised edge which surrounds said chamber [30] ForeignApplication Priority Data and together with the rotatable shaft forms anoutflow Oct 15 1970 Netherlands I I 7015119 gap. The pressure chambersare located partly beside I. each other and overlap each other in thecircumferen- 52 us. Cl. 308/122 The Outflow gaps have a resistance to 51] Int. Cl. Fl6c 17/16 flow which is variable in the circumferentialdirechOh; [58] Field of Search I I i I 308/9 122 A the resistance toflow varies in such manner that the l I I H forces exerted on the shaftby the pressure chambers, [56] References Cited in response to alocalized unevenness with respect to an imaginary line joining thecenter of the bearing to the UNITED STATES PATENTS center of one of thebearing segments. 3.357.759 12/1967 Stephenson 508/122 4 Claims, 7Drawing Figures PATENIED sazsnur's PRIOR ART IN VEN TOR.

ERIC TAPLEY FERGUSON Agent Pmlammwasma 3.761.149

SHEET 2 0f 3 INVENTOR.

ERIC TAPLEY FERGUS M K gent IIYDROSTATIC RADIAL BEARING The inventionrelates to a hydrostatic radial bearing having a shaft which isrotatable in a stationary housing. The housing has bearing segmentswhich are located in pairs opposite to each other and succeed each otherin the circumferential direction. Each bearing segment comprises apressure chamber with a supply duct and a raised edge which surroundssaid chamber forming an outflow gap with the shaft.

Bearings of this type are known but have the disadvantage that when thebearing shaft is not exactly circular, the axis of instantaneousrotation will continually vary relative to the bearing shaft. A highdegree of accuracy of rotation can be obtained only, either by anextremely accurate finish of the bearing shaft, or by considerablyincreasing the number of bearing seg ments. Both solutions are expensiveand the increased number of bearing segments has the additional drawbackof a large number of necessary pre-restrictions, one for each pressurechamber, which easily get clogged.

' It is the object of the invention to overcome these disadvantages andto provide a hydrostatic radial bearing which, in spite of a cheap andsimple construction, has a high degree of accuracy of rotation.

Accordingto the invention this object is achieved in that successivepressure chambers, partly situated beside each other, overlap each otherin the circumferentialdirection. The outflow gaps have a resistance toflow which is variable in the circumferential direction. The forcesexerted on the shaft by two oppositely located pressure chambers as aresult of a localized unevenness are proportional to cos d), tbbeing anangle which denotes the instantaneous angular position of the unevennesswith respect to an imaginary line which joins the center of the bearingto the center of one of the two pressure chambers.

As a result of the overlap of the pressure chambers, an unevenness onthe circumference of the rotating shaft extending in the axial directionsimultaneously influences two pressure chambers. The resultant forceexerted on the shaft by successive pressure chambers as a result of theunevenness, is directed radially, is of a constant value and follows theshaft in its rotary movement. The shaft will rotate truly about aninvariable axis of rotation which coincides with the center of thebearing. r

In oneembodiment of the bearing according to the invention the outflowgaps have a constant radial height, the variable resistance to flowbeing obtained by profiling the axial width of the outflow gaps whichincreases from the center of the bearing segment towards the two ends.By varying the width of the outflow gaps with constant height, thedesired dependence of the forces exerted by the pressure chambers isobtained in a simple manner.

According to a preferred embodiment of the bearing according to theinvention, in which the bearing comprises four bearing segments, eachbearing segment covers substantially half the circumference of thebearing. In contrast with the known bearings, a very high accuracy ofrotation can be obtained with only four bearing segments.

The varying width of the outflow gaps can be ob tained by adapting thewidth of the bearing segments to the required width of the outflow gaps,the width of the pressure chambers being constant. According to afurther preferred embodiment of the bearing according to the invention,however, the width of the pressure chambers decreases from the centertowards the two ends, the bearing segments having a constant outer axialwidth. As a result a simple design of the bearing segments is obtained,while the pressure chambers and the raised edges of varying widthsurrounding said chambers can be profiled in a single operation.

In order that the invention may be readily carried into effect,embodiments thereof will be described in greater detail, by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a known hydrostatic radial bearing;

FIG. 2 is a developed view of the bearing segments of the bearings shownin FIG. 1;

FIG. 3 is a diagrammatic cross-sectional view of an embodiment of thebearing according to the invention;

FIG. 4 is a cross-sectional view of the bearing taken on the line IV--IVof FIG. 6,

FIG. 5 is a cross-sectional view taken on the line V-V of FIG. 6,

FIG. 6 is a developed view of the bearing segments of the bearing;

FIG. 7 is a developed view of another embodiment of the bearingaccording to the invention.

FIGS. 1 and 2 show a known hydrostatic radial bearing having a shaft 1which is rotatable in a stationary housing 3 which comprises fourbearing segments 5 in the sequence X, Y ,-X Y Each bearing segmentcovers substantially a quarter of the circumference of the bearing andcomprises a pressure: chamber 7 around which a raised edge 9 is presentwhich together with the shaft 1 form an outflow gap 11. Each bearingsegment has a duct 13 for the supply of fluid under pressure. Theoutflow gaps have a constant radial height h and a constant axial widthb. i

In the case of a truly circular shaft, each bearing seg ment would exertthe same force F F,,,, F and F from the center of the bearing segment onthe shaft. However, a shaft will usually not be truly circular. Anunevenness on the circumference of the shaft I extending in the axialdirection is shown in FIG. 1 on an exaggerated scale and is denoted by2. When passing the bearing segment X the unevenness Z only influencesthis bearing segment and the force F will increase. As

soon as the unevenness Z traverses the bearing segment Y only thissegment is influenced. The force F "1 increases and the shaft 1 will bedisplaced by the force F,, F g in a direction perpendicular to the forceF F During traversing the other bearing segments, the shaft 1 isdisplaced by them in a similar manner. The axis of instantaneousrotation successively assumes the positions R R,,',, R and R112 denotedin FIG. 1.

FIGS. 3 to 6 show an embodiment of the bearing according to theinvention, the housing 3 of which also comprises four bearing segments XY X and Y The bearing segments X and X, are located in a transverseplane IVIV, while the bearing segments Y, and Y are located in aparallel transverse plane V-V. Each bearing segment covers substantiallyhalf the circumference of the bearing so that two successive bearingsegments will always overlap each other in the circumferential directionover an angle of substantially Each bearing segment comprises a pressurechamber 7 around which an upright edge 9 is present forming an outflowgap 11 with the shaft 1, the gap having a constant radial height h. Incontrast with the known bearing shown in FIGS. 1 and 2, the width b ofthe bearing segments X and X and b of the bearing segments Y, and Yincreases from the center of each pressure chamber in the direction ofthe two ends. It may be assumed that the flow of the bearing liquidthrough the outflow gaps is truly axial. Near the center of eachpressure chamber, the width b and b is small, so the contribution to theliquid supply is large; the unevenness Z will thus have a comparativelylarge influence. Near the ends of the pressure chambers, the width b andb is large and the contribution to the liquid supply thus is small; theunevenness Z will have only a slight influence on the liquid supply.

The unevenness Z simultaneously influences two bearing segments, in theposition shown the bearing segments X and Y,. The bearing shaft 1 willrotate truly about a non-variable axis of rotation R, located on theradius Z if the resultant F of the forces F F and F,,, F, exerted by thebearing segments X and Y for each angle (b occurs in the direction ofand is of constant value. A necessary condition for this is that theforce F F caused by Z is proportional to cos 4: and F F is proportionalto sin 4a.

This condition for the resultant F is satisfied by a suitable choice ofthe width b and b as a function of 4:, in which on an approximation 12,is proportional to l/cos d) and b, to l/sin (b. The shaft 1 is displacedby the constant resultant force F by a fixed amount in the direction 20and rotates about a non-variable axis of rotation R which coincides withthe center 0 of the bearing.

In the embodiment shown in FIG. 6, the bearing segments have a constantaxial width, the width of the pressure chambers decreasing from thecenter towards the two ends.

FIG. 7 shows another embodiment in which the width b, and b, of theoutflow gaps varies similarly, the pressure chambers, however, having aconstant width and the axial width of the bearing segments varying.

The invention is not restricted to bearings having four bearingsegments. In a bearing having 2n bearing segments the pressure chambersare situated stepwise behind each other, n pressure chambers beingsituated beside each other throughout the circumference and each pair oftwo oppositely located pressure chambers being located in a transverseplane. The forces exerted on the shaft by each pair of oppositelylocated pressure chambers as a result of the unevenness are proportionalto cos d), d) being an angle which indicates the angular position of theunevenness with respect to an imaginary line joining the centerv of thebearing to the center of one of the two pressure chambers.

Because of the high degree of accuracy of rotation, the bearingaccording to the invention is suitable for very accurate operations. Thesame accuracy of rotation as of the known bearings can be obtained withsignificantly lower cost. In all bearing constructions according to theinvention the bearing segments located in the same plane can adjoin eachother as is shown in FIG. 6, or be separated by a gap extending in theaxial direction as shown in FIG. 7.

What is claimed is:

1. A hydrostatac radial bearing comprising a stationary housing having ashaft which is rotatable therein, bearing segments in said housinglocated in pairs opposite to each other and succeeding each other in thecircumferential direction, each bearing segment comprising a pressurechamber, a supply duct connected to said chamber, and a raised edgewhich surrounds said chamber and together with the shaft forms anoutflow gap, said successive pressure chambers overlapping each other inthe circumferential direction, the outflow gaps having a resistance toflow which is variable in the circumferential direction, the forcesexerted on the shaft by two oppositely located pressure chambers inresponse to a localized unevenness being proportional to cos qb, beingan angle which denotes the instantaneous angular position of theunevenness with respect to an imaginary line joining the center of thebearing to the center of one of the pressure chambers.

2. A hydrostatic radial bearing as claimed in claim 1, wherein theoutflow gaps have a constant radial height, the axial width of theoutflow gaps being profiled so as to increase from the center of thebearing segments towards the two ends thereby providing the variableresistance to flow.

3. A hydrostatic radial bearing as claimed in claim 2, having fourbearing segments, wherein each bearing segment covers substantially halfthe circumference of the bearing.

4. A hydrostatic radial bearing as claimed in claim 1 wherein the widthof the pressure chambers decreases from the center towards the two ends,the bearing segments having a constant outer axial width.

1. A hyDrostatac radial bearing comprising a stationary housing having ashaft which is rotatable therein, bearing segments in said housinglocated in pairs opposite to each other and succeeding each other in thecircumferential direction, each bearing segment comprising a pressurechamber, a supply duct connected to said chamber, and a raised edgewhich surrounds said chamber and together with the shaft forms anoutflow gap, said successive pressure chambers overlapping each other inthe circumferential direction, the outflow gaps having a resistance toflow which is variable in the circumferential direction, the forcesexerted on the shaft by two oppositely located pressure chambers inresponse to a localized unevenness being proportional to cos phi , phibeing an angle which denotes the instantaneous angular position of theunevenness with respect to an imaginary line joining the center of thebearing to the center of one of the pressure chambers.
 2. A hydrostaticradial bearing as claimed in claim 1, wherein the outflow gaps have aconstant radial height, the axial width of the outflow gaps beingprofiled so as to increase from the center of the bearing segmentstowards the two ends thereby providing the variable resistance to flow.3. A hydrostatic radial bearing as claimed in claim 2, having fourbearing segments, wherein each bearing segment covers substantially halfthe circumference of the bearing.
 4. A hydrostatic radial bearing asclaimed in claim 1 wherein the width of the pressure chambers decreasesfrom the center towards the two ends, the bearing segments having aconstant outer axial width.